1. Field of the Invention
The present invention relates to a transgenic plant which exhibits resistance to at least one disease. In particular, the present invention relates to a transgenic plant which comprises an expression cassette including a thionin gene and being capable of expressing the thionin gene, and which exhibits resistance to at least one disease.
2. Description of the Related Art
In the field of agricultural production, there has been a general desire for stable production of high quality plants and reduction of dependency on agricultural chemicals. Accordingly, plant species exhibiting resistance to pests and pathogenic microbes have been vigorously improved, bred, and developed, by utilizing useful plant biotechnology techniques, e.g., plant cell fusion techniques and recombinant DNA techniques.
In fact, a transgenic plant exhibiting resistance to herbicides (Japanese Laid-open Publication No. 2-186925), a transgenic plant exhibiting resistance to viruses (Japanese Laid-open Publication No. 4-330233), and a transgenic plant exhibiting resistance to pests (Japanese Laid-open Publication No. 3-247220) have already been produced by employing recombinant DNA techniques.
Furthermore, several kinds of transgenic plants which exhibit resistance to plant pathogenic microbes have been produced, e.g., a transgenic plant which exhibits resistance to pathogenic filamentous fungi by the introduction of a gene encoding an enzyme which inactivates the toxins produced by pathogenic filamentous fungi (Anne S. Ponstein et. al., Plant Physiology, 104: 109-118, 1994), and a transgenic plant which exhibits resistance to at least one pathogenic microbe by the introduction of a gene encoding an antimicrobial protein from an insect (Japanese Laid-Open Publication No. 7-250685).
The inventors isolated from leaves of Avena sativa a novel thionin, which is an antimicrobial protein, sequenced a gene encoding the thionin by a known method, and attempted transformation of a tobacco plant using the thionin gene (Japanese Laid-open Publication No. 8-266279). A transformed, redifferentiated tobacco plant has been obtained through this attempt.
However, it is not guaranteed that all transgenic plants will become practical and useful plants exhibiting high disease resistance because factors such as the species of the plant, transformation methods, expressed amounts and expression sites of the introduced genes, and influences of the gene products on the plant may vary the disease resistance or impede growth. Furthermore, it is known that it depends on each situation whether or not the acquired disease resistance will be stably passed down to progenies. For these reasons, it has been desired to produce a practical and useful plant exhibiting high disease resistance.